---
tags: JS 直播班 - 2022 秋季班
---
# 🏅 Day 36 - 箭頭函式

### 寫法
宣告變數、並賦予它函式，我們稱這段 code 為「 函式表達式 」，下方範例都屬於函式表達式。
在 ES6 函式表達式中我們可以將 `function` 關鍵字移除並在參數後加入箭頭 `=>` 將程式碼簡化，此時即為箭頭函式。

/* 傳統函式 */
let cat = function(name){
  return `我的貓貓叫 ${name}`;
};
console.log(cat('Miu'));       // "我的貓貓叫 Miu"


/* 箭頭函式 */
let arrowCat = (name) => {     // function 改為 =>
  return `我的貓貓叫 ${name}`;
};
console.log(arrowCat('Miu'));  // "我的貓貓叫 Miu"

若是當 `{ }` 內程式碼只有一行時，則可以再簡化：

// 將 return 以及 {} 移除，簡化成一行，此時自動會有 return 的作用
let arrowCat = (name) => `我的貓貓叫 ${name}`;
console.log (arrowCat('Miu'));  // "我的貓貓叫 Miu"

> **注意：**
> 由於 `{}` 大括號內可以加入多行程式碼，所以寫成一行但沒有移除大括號時不會自動帶入 return：
> ```javascript=
> let calcPlus = (num) => num + 1;
> let calcPlusNoReturn = (num) => { num + 1 }; // 不會自動帶入 return
>
> // 比較
> let calcPlusSum = calcPlus(3);
> let calcPlusNoReturnSum = calcPlusNoReturn(3);
>
> console.log(calcPlusSum); // 4
> console.log(calcPlusNoReturnSum); // undefined
> ```

若是當只有一個參數時，我們可以再簡化，將參數旁的小括號 `()` 移除：

// 移除 () 
let arrowCat = name => `我的貓貓叫 ${name}`;
console.log (arrowCat('Miu'));  // "我的貓貓叫 Miu"

> **注意：**
> 若沒有參數，不能移除 `()`
> ```javascript=
> let sayHello = () => `Hello!`;
> sayHello(); // Hello!
> ```

問題
---
試著用箭頭函式寫寫看 forEach 吧！

let pokemon = ['呆呆獸','沼王','噴火龍','雷丘'];
pokemon.forEach(function(item, index) {
 console.log(`${index+1} : ${item}`);
})

## 回報流程

將答案寫在 CodePen 並複製 CodePen 連結貼至底下回報就算完成了喔!
解答位置請參考下圖（需打開程式碼的部分觀看）


<!-- 解答：

let pokemon = ['呆呆獸','沼王','噴火龍','雷丘'];

pokemon.forEach((item, index) => { 
  console.log(`${index+1} : ${item}`);
});

-->

回報區
---

| Discord | CodePen / 答案 |
|:---------------------:|:----------------------------------------------------------------------------:|
| YC#2522 | [CodePen](https://codepen.io/YCLu/pen/PoaEapX) |
| yumy#1940 | [CodePen](https://codepen.io/yumyyang/pen/jOKYKwO) |
| SASIMI#5099 | [codepen](https://codepen.io/sashimi1327/pen/LYrerLO) |
| PayRoom#8328 | [CodePen](https://codepen.io/water38198/pen/jOKYKGE) |
| shinyhung#3825 | [CodePen](https://codepen.io/sean_1215/pen/XWYVYVM?editors=1011) |
| AuroraC#6539 | [codepen](https://codepen.io/AuroraC/pen/JjZMZpO?editors=1012) |
| 圈圈#4060 | [codepen](https://codepen.io/wjejfczn-the-bold/pen/LYrerQQ) |
| kenki100#0068 | [Codepen](https://codepen.io/ken100/pen/zYapajz) |
| RJRS#9430 | [CodePen](https://codepen.io/RJRS/pen/YzvYvLO) |
| albee#9121 | [Codepen](https://codepen.io/albee-chang/pen/BaVJVxg?editors=1011) |
| Peng#9811 | [CodePen](https://codepen.io/peng-027/pen/mdKpKKa) |
| 楓之聲#6945 | [Codepen](https://codepen.io/sshane258/pen/RwJxJYE) |
| WEI_RIO#9342 | [Codepen](https://codepen.io/wei_wu/pen/dyKJKQj?editors=1011) |
| 大衛#4869 | [Codepen](https://codepen.io/exnsrpjc/pen/poKpKxb?editors=0010) |
| Data#9297 | [Codepen](https://codepen.io/kirakira72/pen/QWxaxZj) |
| 威0#6919 | [codepen](https://codepen.io/n0918679182/pen/LYrerze?editors=0011) |
| 軟綿綿 (๑•ᴗ•๑) ♡#3627 | [CodePen](https://codepen.io/Connie-Chien/pen/poKpZvR?editors=1010) |
| 法希娜#3206 | [CodePen](https://codepen.io/yiiserpf-the-encoder/pen/WNydKRo?editors=1011) |
| mandylai#4055 | [CodePen](https://codepen.io/mandy-lai-2/pen/poKpZRw) |
| LHchien33#6232 | [CodePen](https://codepen.io/lin_chien/pen/jOKYpBB) |
| jacky010080#0880 | [CodePen](https://codepen.io/Yen-Jung-Chen/pen/qBKpypv?editors=1011) |
| amy芳#1385 | [CodePen](https://codepen.io/amy-chieng/pen/LYreBev) |
| kuku#3118 | [Codepen](https://codepen.io/mengting-ku/pen/eYKyjVr) |
| yawun#0042 | [CodePen](https://codepen.io/monicalin/pen/WNydKJj) |
| 威爾#1694 | [CodePen](https://codepen.io/WILL_Wu/pen/VwdyBBZ) |
| 柔柔#1716 | [Codepen](https://codepen.io/rouchen/pen/KKeZBxy?editors=1011) |
| Hilda#7085 | [Codepen](https://codepen.io/vwquikad-the-vuer/pen/QWxaBXa) |
| banazita#5143 | [CodePen](https://codepen.io/banazita/pen/RwJxJdv?editors=1111) |
| CofCat#9226 | [CodePen](https://codepen.io/cofcat456/pen/bGKaxbo?editors=1011) |
| Ruby Chen#7452 | [CodePen](https://codepen.io/ruby92429/pen/zYapJxX?editors=1011) |
| Kimi #9564 | [CodePen](https://codepen.io/kimihu91/pen/mdKpjNE) |
| 心幻羽#0056 | [CodePen](https://codepen.io/linglingsyu/pen/JjZMmGW?editors=1111) |
| JackC#0411 | [CodePen](https://codepen.io/key0329/pen/PoaEyzy) |
| Rr#2215 | [Codepen](https://codepen.io/rufangcheng/pen/PoaEymX) |
| Yuna Huang#2692 | [CodePen](https://codepen.io/Yuna1002/pen/gOKoBpj?editors=1111) |
| Winnie#1306 | [Codepen](https://codepen.io/WinnieWuWinnie/pen/PoaEyXv?editors=1111) |
| 黑白兔#0684 | [Codepen](https://codepen.io/johnny329/pen/xxzpyeY) |
| m_m#5493 | [CodePen](https://codepen.io/minnn7716/pen/RwJxeOv) |
| Clara#1275 | [CodePen](https://codepen.io/bsupixqu/pen/WNydYwx?editors=0010) |
| k.sin#3115 | [CodePen](https://codepen.io/sin588/pen/wvXpQxg?editors=0012) |
| masterYan#2480 | [CodePen](https://codepen.io/htzwgoqt-the-looper/pen/BaVJGOQ?editors=1011) |
| jackson204#6363 | [CodePen](https://codepen.io/jackson204/pen/YzvYRRP?editors=1111) |
| Tami#6742 | [CodePen](https://codepen.io/wqsdqbjn-the-vuer/pen/rNKpQqZ) |
| Potatolee#7749 | [CodePen](https://codepen.io/potatoleee/pen/RwJxqyN?editors=1011) |
| Arista#5802 | [CodePen](https://codepen.io/arista-hsieh/pen/yLEpQmE) |
| 小白#2406 | [CodePen](https://codepen.io/gracewhite/pen/xxzpQNN) |
| 粉蒸肉#6214 | [Codepen](https://codepen.io/wrightyu/pen/eYKybWo?editors=1011) |
| jimmyFang#9575 | [Codepen](https://codepen.io/pohxiqqo/pen/oNypmBo) |
| Hironaka#7367 | [Codepen](https://codepen.io/Hironaka0815/pen/mdKpvwG?editors=1111) |
| 勁辣雞腿寶#5817 | [Codepen](https://codepen.io/orz311013/pen/vYrpbqb?editors=1111) |
| hannahTW#2224 | [Codepen](https://codepen.io/hangineer/pen/LYreqor?editors=1112) |
| 雷雷#7844 | [Codepen](https://codepen.io/lei-yi-jie/pen/dyKJrGw?editors=0011) |
| beta lin#1445 | [CodePen](https://codepen.io/linbeta/pen/GRGyeZV) |
| Amberhh#2465 | [Codepen](https://codepen.io/Amberhh/pen/abKEKME) |
| 無名#6427 | [Codepen](https://codepen.io/Nomoney/pen/qBKpwKZ) |
| Sentiments#4883 | [codepen](https://codepen.io/Sentiments/pen/gOKoyEv?editors=0011) |
| 出事了阿伯#9923 | [codepen](https://codepen.io/BradpittLai/pen/WNydBYb?editors=1011) |
| 肉桂卷#0625 | [codepen](https://codepen.io/ginnlee/pen/RwJxzdW?editors=0011) |
| mou#2215 | [codepen](https://codepen.io/shihchiehlan/pen/xxzpvJw?editors=0010) |
| Loran#1105 | [codepen](https://codepen.io/loranlin/pen/rNKJWPy?editors=1111) |
| azami#5986 | [Codepen](https://codepen.io/azami/pen/gOKvgwV) |
| Benson#6763 | [Codepen](https://codepen.io/kumashow/pen/PoaQWJw) |
| 薯餅#3581 | [Codepen](https://codepen.io/ColdingPoTaTo/pen/ExRQZrO) |
| KC_8685#9343 | [Codepen](https://codepen.io/cathy7411/pen/KKeQaEy) |
| Lucie#3831 | [Codepen](https://codepen.io/bisespei/pen/abKqJwe) |
| William Lai#0196 | [Codepen](https://codepen.io/lai-weihan/pen/YzveEQg) |
| Cream#3449 | [Codepen](https://codepen.io/lai-weihan/pen/YzveEQg) |
| yoyo#1003 | [Codepen](https://codepen.io/pen/MWXQQdj?editors=1111) |
| Shuo#1596 | [Codepen](https://codepen.io/chiangchungshuo/pen/NWzOgxa?editors=1010) |
| Cliff#4606 | [Codepen](https://codepen.io/Cliff_hex/pen/QWxZJNO?editors=0011) |
| charlottelee849#0366 | [Codepen](https://codepen.io/char849/pen/xxzyMNm?editors=0012) |
| suihsilan#9485 | [Codepen](https://codepen.io/suihsilan/pen/vYrQXJW?editors=0010) |
| Yishan#4902 | [Codepen](https://codepen.io/gdjrehhw-the-animator/pen/OJEdgNL?editors=0012) |
| Paul#7426 | [CodePen](https://codepen.io/paul-1997/pen/yLEjBpW) |
| 狸貓#5863 | [CodePen](https://codepen.io/tanuki320/pen/GRGeLRR?editors=1010) |
| Mia小福#4473 | [CodePen](https://codepen.io/a0950271/pen/JjZVaEe) |
| hungya#0773 | [CodePen](https://codepen.io/hungya777/pen/KKeYGax?editors=0011) |
| cbs#9007 | [Codepen](https://codepen.io/wasdjk/pen/bGKPqKE) |
|yaru#6308|[CodePen](https://codepen.io/lszaietc/pen/oNyEppj)|
|蓁心#6229|[CodePen](https://codepen.io/tlorfrnl-the-typescripter/pen/eYjOGgG?editors=1011)|
|阿蘇#8531|[CodePen](https://codepen.io/susu3131/pen/KKBKray?editors=1011)|
|J_u_d_y#5993|[Codepen](https://codepen.io/J_u_d_y/pen/vYzJZyY?editors=1111)|
|Bingsu#2362|[Codepen](https://codepen.io/pmyfr/pen/poxJBoN?editors=1111)|